EVIDENCE OF EVOLUTION Evolutionary Theories

LAMARCK Developed two theories of evolution: Law of Use and Disuse: the more a part is used, the stronger it becomes Inheritance of Acquired Characteristics: theory stating that useful traits developed during a lifetime are passed on to offspring

EXAMPLES

Children of cyclists inherit the strong muscles of their parents

WEISMAN Disproved Lamarck’s theory that acquired traits could be inherited by cutting off the tails of mice then mating them RESULT: offspring of tailless mice were always born with normal length tails

MALTHUS Believed that human population increased geometrically (2, 4, 8, 16) Food production increased arithmetically (1, 2, 3, 4) RESULT: millions of people must die to keep a balance between the need/supply of food

DARWIN Background Information: Traveled for five years aboard the HMS Beagle Made significant discoveries by studying finches on the Galapagos Islands RESULT: noticed that species on island resembled mainland species, but had adapted to different regions

THEORY OF NATURAL SELECTION Nature acts as a selecting agent of an organism’s traits Organisms better adapted to the environment survive and reproduce more successfully than organisms that are not as well adapted Overall theme: traits that help an organism survive in a changing environment are passed on to offspring

DARWIN’S MAIN IDEAS Overproduction: a population generally produces more offspring than can survive in an environment

COMPETITION Definition: there is a struggle between organisms for space, food, water, light, minerals, and other limited resources

VARIATION Definition: members of a population show differences in traits that make certain individuals better adapted to survive Types of variations—differences in size, structure, color, etc.

NATURAL SELECTION Some variations are more helpful than others—there is a natural selection against organisms that cannot adapt Organisms that cannot adapt die

SURVIVAL OF THE FITTEST Applies to those individuals that have variations that enable them to live and reproduce

INHERITANCE OF VARIATIONS Organisms with more helpful variations are more likely to survive and reproduce, passing on variations to offspring

EVOLUTION OF NEW SPECIES Variations accumulate over long periods of time Eventually, there are so many variations, a new species evolves